Objective To investigate the roles of Smad7 and histone deacetylase 1(HDAC1) in the development of aristolochic acid nephropathy (AAN), we studied their expressions in AAN. Methods The expressions of Smad7 and HDAC1 in the AAN and control groups were measured by immunohistochemical technique, Western blotting and RT-PCR. A total of 32 male mice were randomized into four groups. Aristolochic acid(AA)Ⅰ was dissolved in PBS and was given to mice in three treatment groups through intragastric administration ［4 mg/（kgI>&#/I>8226;d）, 8 mg/（kgI>&#/I>8226;d）, and 16 mg/（kgI>&#/I>8226;d）,respectively］. Results The immunohistochemical positive reaction for HDAC1 was distributed in the epithelial cell nuclei of the renal tubules. The expression level of HDAC1 was significantly higher in the AAN group than that in the control group. The results of Western blotting and RT-PCR showed that the protein expression of Smad7 in the AAN group was significantly lower than that of the control group, while the situation was opposite for HDACl expression. Conclusion